im Englischen scheint sich missionary work ohne nähere Bezeichnung durchgesetzt zu haben. Dass diese Arbeit im oben genannten Fall von einer Diakonie ausgeht, wird vermutlich aus dem übrigen Text herausgehen oder muss irgendwie separat angefügt werden.
Für missionary work gibt es jede Menge Referenzen in Google

he began with charitable work to help the blind, the sick
Missionary sounds like preaching and social welfare sounds a bit too official. The Diakonie-bit doesn't really have to be translated, the context is quite clear.

German term (edited): missionsdiakonische Arbeit f�r...

During the Second World War, a group of British servicemen based in Palestine, began supporting the Mission to the Blind in Bible Lands founded by British missionary, Mary Lovell,
http://www.biblelands.org.uk/about_us/history/
Won't you please pray for this missionary family and for this mission to the blind and visually handicapped around the world on a daily basis?
http://www.biblesfortheblind.org/aboutus.shtml
Hildesheim Mission to the Blind (HVBC)
http://ricci.rt.usfca.edu/institution/view.aspx?institutionI...

This appears to be one of those occasions where English is more concise than German



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Note added at 5 hrs 6 mins (2005-04-06 01:04:27 GMT)
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Die Christoffel-Blindenmission sieht sich auf diese Tradition gegründet und hält sie lebendig: „Der Verein führt das Werk von Pastor Ernst J. Christoffel fort, der 1908 im Orient die missionsdiakonische Arbeit für Blinde, anders Behinderte, Kranke und Notleidende begann. Er versteht sich als eine Dienstgemeinschaft von Christen verschiedener Glaubensprägung, die in der Nachfolge Jesu Christi die Botschaft von der Liebe Gottes in Wort und Tat verkündigen
http://www.christoffel-blindenmission.de/beitrag/CBM_DE_Basi...

I see the problem. You have already used ‘Mission to the Blind…’ in the previous sentence! (The Christoffel Mission to the Blind…)

Perhaps you might wish to consider ‘humanitarian missionary work’

Schweitzer, Albert: A French theologian, student of music, and physician of the twentieth century. Schweitzer received many awards for his humanitarian missionary work in Africa, including the Nobel Prize for peace.
http://www.answers.com/topic/albert-schweitzer
They have been performing humanitarian missionary work even before 1971. In 1960, Christian missionaries opened a maternity hospital in the Emirate of Abu Dhabi; the hospital continues to operate.
http://www.uaeinteract.com/news/default.asp?ID=178
YTM has organized a national mission in Chicago for the week prior to the Regnum Christi Youth and Family Encounter July 12-20, 2003. The mission program will focus on two parish communities and humanitarian missionary work with youth of Chicago,
http://www2.legionofchrist.org/eng/articulos/articulo.phtml?...